Marking email as spam

When PostJobFree user marks our email as spam in their email inbox (e.g. on yahoo, gmail or aol) - we delete that user account from PostJobFree.
In addition, we blacklist such email and do not allow creating another account with such email.

The reason behind it is to improve email deliverability to the inboxes of users who actually want to receive our emails.

So, when PostJobFree visitor is trying to create new account with blacklisted email, PostJobFree shows:
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We blacklisted your johndoe@aol.com email because on 2015-11-30 16:28:27 UTC you marked email PostJobFree sent to you as spam in your @aol.com inbox.
Could you please let us know at support@postjobfree.com why you marked our email as spam?
Meanwhile you may try using another email.
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Yesterday I received angry email from blacklisted user:
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I tried to apply to a job today. The posting was from Beyond. I got an ugly message from you that said 8 months ago I listed one of your e-mails on AOL as spam and you blacklisted my e-mail address. You wanted to know why I listed you e-mail as spam. Since the incident you supposedly listed was 8 months ago I have no idea what you are talking about, nor would I remember any information.

I made a complaint to AOL.
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How should I reply to that angry blacklisted user?

Update 1:
How to get spam reports feedback

Update 2:
====================
From: Dennis Gorelik <support@postjobfree.com>
To: johndoe <johndoe@aol.com>
Sent: Thu, Jul 28, 2016 8:33 am
Subject: Re: Your e-mail

Could you please forward your AOL complaint (and their reply, if any) to me?

My concern is that if you randomly marked our email as spam in the past - it will keep happening in the future.
====================
From: johndoe <johndoe@aol.com>
To: support@postjobfree.com
Date: Thursday, July 28, 2016, 10:20:47 AM
Subject: Your e-mail

1. No reply from AOL, did not expect one.

2. If I had listed your site as spam none of your other e-mails, including this one, would have made it to me.

3. If you blacklisted my e-mail 8 months ago, why have I not seen anything until yesterday.

4. Remove my name from your system.
====================

Bottom line: it rarely makes sense to deal with angry users.
The only real benefits from such communications are learning and entertainment.